1. Technical Field
The present invention relates to a technology for generating animation, and more particularly, to a technology for generating animation corresponding to a user's sketch input.
2. Description of the Related Art
A 3-dimensional (3D) virtual character has been widely used in digital content fields such as movie, game, and virtual environment. Generally, to produce animation including the virtual character, a key-framed scheme for using a posture of a 3D character model articulated by multiple joints as a main frame has been mostly used. According to the key-framed scheme, if the user directly edits the posture of the model, an animation system includes a process of automatically generating in-between frames. Accordingly, the key-framed scheme has an advantage in that the user may freely generate his/her wanted style of character animation but requires a lot of user's efforts and time since a process of producing a motion posture corresponding to the main frame requires a repetitive editing process for the following reason. First, since an articulated skeleton forming the character model has a high degree of freedom, to perform a process of controlling, by a user, a large number of joints to generate a high quality of motion posture, professional training and physical knowledge on a motion of a human body are required. Second, to show natural character animation, a motion posture more than 24 frames per second needs to be generated. To this end, even a professional animator takes up much time to edit a main posture. Third, most 3D modeling tools for editing the motion posture has a complex editing process and a user interface. Therefore, general users can hardly produce a high quality of animation using the 3D modeling tools. For the reasons, to produce the high quality of 3D character animation by the current key-framed scheme, a larger number of animation experts are required to produce even animation having a short length.
A motion capture scheme developed to overcome some of the disadvantages of the key-framed scheme is a technology for tracking motions of an actor using a plurality of cameras when the actor directly takes the motion of the virtual character and then recovering them to 3D motion data. The motion capture scheme may be used for the 3D character animation production pipeline by fitting an articulated skeleton to the motion-captured 3D motion data. Since the motion data generated by the motion capture scheme are generated by the scheme of directly capturing a motion of an actor, the motion capture scheme may guarantee very realistic animation but for the following reasons, it is difficult to reuse the data as other purposes. First, since the motion data generated while a motion is captured more than 24 frames per second in response to a camera speed have high continuity and density of a frame, if the user edits the captured data, physical validity that is an important factor of the motion included in the continued frames may be easily broken. Therefore, when the captured data are edited based on the user's desired style of motions, quality degradation in results may easily occur due to motion unnaturalness and motion noise. Second, generally, a motion capture system for tracking and recovering a high quality of motion data is very expensive and requires a wide space as well as may be used only by many operating personnel who get professional education. Finally, in the motion capture scheme, a factor most affecting the motion quality is an actor's skill. In particular, a high quality of motion data for complex and dynamic motions such as dance or exercise are hardly extracted from motions of the general public. Therefore, to produce various 3D character animations by using the motion data generated by the current motion capture scheme, a tool and a motion editing expert for professionally editing the captured data are required.